Response dynamics of rat barrel cortex neurons to repeated sensory stimulation

Ehsan Kheradpezhouh,Mehdi Adibi,Ehsan Arabzadeh

doi:10.1038/s41598-017-11477-6

Abstract

Neuronal adaptation is a common feature observed at various stages of sensory processing. Here, we quantified the time course of adaptation in rat somatosensory cortex. Under urethane anesthesia, we juxta-cellularly recorded single neurons (n = 147) while applying a series of whisker deflections at various frequencies (2–32 Hz). For ~90% of neurons, the response per unit of time decreased with frequency. The degree of adaptation increased along the train of deflections and was strongest at the highest frequency. However, a subset of neurons showed facilitation producing higher responses to subsequent deflections. The response latency to consecutive deflections increased both for neurons that exhibited adaptation and for those that exhibited response facilitation. Histological reconstruction of neurons (n = 45) did not reveal a systematic relationship between adaptation profiles and cell types. In addition to the periodic stimuli, we applied a temporally irregular train of deflections with a mean frequency of 8 Hz. For 70% of neurons, the response to the irregular stimulus was greater than that of the 8 Hz regular. This increased response to irregular stimulation was positively correlated with the degree of adaptation. Altogether, our findings demonstrate high levels of diversity among cortical neurons, with a proportion of neurons showing facilitation at specific temporal intervals.

Highlights

Neuronal adaptation is a common feature observed at various stages of sensory processing
We applied a series of brief whisker deflections of constant amplitude to produce cortical responses to discrete stimuli with well-defined time course and quantified the profile of adaptation for individual neurons recorded across layers of the vS1 cortex
This decrease in the net neuronal response was observed despite the fact that at higher frequencies the neuron’s principal whisker was stimulated with a higher number of deflections during the 3-s trial duration (96 deflections at 32 Hz compared to 6 deflections at 2 Hz)

Summary

Introduction

Neuronal adaptation is a common feature observed at various stages of sensory processing. Similar homeostatic effects have been observed in the primary visual cortex of anesthetized cats[35] where adaptation decorrelated neurons and maintained their population responding rate. This evidence suggests that along with the intrinsic properties of individual neurons[36,37,38], the network properties play a key role in the dynamics of sensory adaptation. We applied a series of brief whisker deflections of constant amplitude to produce cortical responses to discrete stimuli with well-defined time course and quantified the profile of adaptation for individual neurons recorded across layers of the vS1 cortex. We quantify how this tradeoff determines the frequency at which the neurons elicit their maximum response

Methods

Results

Conclusion